1890.] ON THK MARINE MOLLUSCA OF ASCENSION ISLAND. 31] 



Fig. 20. Cylichna remissa, p. 312. 



21. Turbo {Collinia) incertus, p. 311. 



21 a. (-: ) ; upper view. 



22. Scissurella jueunda, p. 311. 



22 a. ; upper surface. 



23. Kcllia crassiuscuta, p. 313. 



24. atlantica, p. 313. 



25. Monfacuta subiriangularis, p. 313. 



26. Crenella pura, p. 314. 



4. On the Marine Mollusca o£ Ascension Island. 

 By Edgar A. Smith. 



[Eeceived March 14, 1890.] 



In the following list of forty-two species of Mollusca from Ascen- 

 sion Island, nine, obtained by the 'Challenger' Expedition, ought 

 not perhaps to be included in the fauna ; for, although dredged 

 close to the island off the west coast, they were from a depth of 

 420 fathoms. 



The poverty of this list is doubtless due to the fact that no 

 experienced collector has ever explored the shores. 



Fourteen of these species occur at St. Helena, eleven are West- 

 African, twelve are found at the Cape Verde, Canary Islands, and 

 the Azores, nine are Mediterranean, and seventeen, or about 40 per 

 cent., are West-Indian forms. These figures, on comparison with 

 those referring to the species found at St. Helena, and given in the 

 previous report, show that the relationship of the two faunas to 

 other regions is the same. Both resemble that of the West Indies 

 more than any other locality, both have a considerable percentage 

 of species common to West Africa, to the Atlantic Islands, including 

 the Cape Verdes, Canaries, Madeira, and the Azores, and also to the 

 Mediterranean, the causes which have effected this distribution 

 doubtless being the same in both cases. 



The three species of Marginella are well-known Cape forms, and 

 therefore the question arises, whether these shells may not have 

 drifted to Ascension on floating tangles as in the case of numerous 

 species at St. Helena. 



A few species are eastern forms, for example Ostrea cucullata 

 and Malleus regula. Both of these, I believe, are established at 

 Ascension. The former was quoted by Chemnitz more than a 

 hundred years ago, and although he remarks that ships returning 

 from China and the East Indies used to call at Ascension for water, 

 I do not think it likely that the shells were carried there from the 

 east. The single valve received from Dr. Conry is in very fresh 

 condition and has not the appearance of having been rolled on the 

 beach. 



In the ' Universal Conchologist ' Martyn has figured a small 

 specimen of the well-known Fusus proboscidi^erus of Lamarck, 

 under the name of Buccinum incisum, and gives as the locality 

 " Ascension Island, new Guinea." 



Proc. Zool. Soc— 1890, No. XXII. 22 



